As technologies progress, an organic light emitting display (OLED) has become one of the most potential future displays. A conventional OLED includes a metal cathode and a transparent anode, and an organic layer is interposed between the cathode and the anode. The metal cathode is made of metal having a low work function, such as Mg, Al or alloy thereof while the transparent anode is made of Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO). Light exits from the organic layer through the transparent anode, which is called “back emission”.
For integrating the organic light emitting display, a controlled circuit, such as an active matrix utilizing thin film transistors (TFT), has to be arranged under the anode. In that case, the aperture ratio decreases as the OLED emits light from the anode. To solve the problem, a top emission construction of the OLED was proposed. FIG. 1 illustrates an active matrix OLED. The organic layer 106 is disposed between the transparent anode 108 and the transparent cathode 104. The cap layer 102 is disposed on the transparent cathode 104. The TFT 306 is coupled to the transparent anode 108 via the electronic connection unit 308 for controlling the light emitted from the organic layer 106.
However, light from the organic layer emits in all direction. If light is not emitted toward the transparent cathode, power is consumed and brightness of the OLED cannot be improved. A demand for an OLED with improved emission efficiency and brightness therefore derives.